The brake calipers are usually fixedly connected to a support structure that stays still with respect to the disc, like for example a spindle of a vehicle's suspension.
In a typical arrangement, one of the two elongated elements has two or more portions for attaching the body of the caliper to the support structure, for example by foreseeing slots or eyelets, for example arranged axially, or through holes, for example arranged radially, suitable for receiving screws for fixing the caliper that, with their ends are received in threaded holes foreseen on the support of the caliper.
In a typical caliper body construction, the elongated elements arranged facing the braking surfaces of the disc are connected together by bridge elements arranged astride of the disc.
The caliper comprises different components mounted on the body such as the pistons, gaskets, bleeding devices and brake fluid supply ducts.
Typically, the body of the caliper is made from metal, like for example aluminium, aluminium alloy or steel. The body of the caliper can be obtained by casting, but also by mechanical chip-removal processing, as well as by forging.
The body of the caliper can be produced both in a single piece or enbloc, and also in two half-calipers typically connected together along a plane that usually coincides with the middle plane of the disc on which the caliper is arranged astride.
In the case in which the driver of the vehicle wishes to brake or slow down the speed of the vehicle, he applies a pressure on the brake pedal, in the case of an automobile. Such pressure on the brake pedal, through a brake pump, exerts a pressure of the brake fluid that through a duct applies to the brake fluid present in the hydraulic circuit arranged inside the body of the caliper until it reaches the cylinders where the pressure is exerted on the surface of the bottom of the pistons forcing them to clamp against the pads, which in turn abut against the braking surfaces of the disc.
The pressure action of the brake fluid also acts on the bottom wall of the cylinder causing a reaction in the body of the caliper that deforms it away from the surfaces of the disc. This deformation of the body of the caliper leads to an increase in the stroke of the pistons and thus to an increase in the stroke of the brake pedal.
The body of the caliper also deforms as a function of the torque exerted by the action of the pistons that abut the pads against the braking surfaces of the disc applied in directions that form torque arms with respect to the attachment points of the caliper body to its support. These torques deform the caliper body also in a tangential and radial direction with respect to the disc, as well as in the axial direction.
The caliper body must therefore have a sufficient structural rigidity, so as to ensure that this deformation of the body of the caliper caused by the braking action is kept within tolerable values, which, as well as avoiding damage to the braking system, do not give the driver the feeling that the braking system is spongy, determining an extra stroke of the lever or pedal of the braking system creating the feeling of a spongy braking system. This requirement pushes towards having extremely rigid structures for the bodies of the calipers and thus towards increasing their bulk and weight.
On the other hand, the body of the caliper, since it is fixedly connected to the vehicle's suspension and is arranged astride of the disc, is one of the non-suspended masses that it is wished to reduce as much as possible to increase the performance of the vehicle.
Of course, these considerations are pushed to the extreme when the vehicle is for racing and the user wants to have a braking system that is extremely responsive to his commands and at the same time extremely light so as not to penalize the performance of the racing vehicle.
There is therefore a need for a caliper body for a disc brake that has improved structural characteristics for the same weight of the body of the caliper, or else that has a lower weight with respect to the solutions of the prior art for the same structural characteristics.
Solutions of caliper bodies are known that are specially researched to increase the characteristics of structural rigidity. For example, patent application EP-A-2022999, patent application EP-A-153497, American patent U.S. Pat. No. 6,708,802, European patent EP-A-1911989, international patent application PCT/EP2005/050615, Japanese patent application JP-A-09257063 and American patent U.S. Pat. No. 3,183,999 all have solutions of brake caliper bodies equipped with reinforcing elements, for example arranged around the caliper bodies. In some of these known solutions the caliper body is of the symmetrical type according to planes passing through the axis of the disc or through the middle of the disc. In other solutions the caliper body has big and distributed windows, also passing right through, which form elongated reinforcing elements arranged longitudinally to the body of the caliper.
Although satisfactory from many points of view, these known solutions nevertheless do not make it possible to obtain structures that maximize the structural rigidity of the body of the caliper reducing weights and at the same time capable of keeping the bulk as low as possible so as to make it easier to mount the body of the caliper even inside the rim and wheel on which brake discs having a large diameter are mounted.